Diaphragm



A.F.NAIHAN.

DIAPHRAGM.

APPLICATION FILED APII. 29, Iszo.

Patented Apr. 18, 1922'.

UNITED siwrssv PATENT FFIC.

ALBERT '.F. NATHAN, OF PLAINFIELD, NEW JERSEY.

DIAPHRAGM.

Specication of Letters Patent. Patented Alil. 18, 1922.

Application filed-April 29, 1920. Serial No. 377,634.

the county of Union and State of New Jersey, have invente-d an Improved Diaphragm,

of which the following specification is a full disclosure.

This invention deals with an improved diaphragm for the sound box of a phonograph, and it consists of two external plates of vitreous material, such as glass, intimately adhering to an intervening sheet of a dissimilar material such as celluloid.

It has heretofore been proposed to use-a slmpleI plate or sheet of glass as a diaphragm, on account ofthe well-known acoustical properties of this material but great difficulty has beenexperienced in a practical sense, owing to the fragile nature of glass. Other Substances, such as mica, wood, parchment, and the like, have therefore been proposed and extensively usedd; a chief advantage residing in their non-fragile character. It is difficult to obtain mica of a perfectly uniform nature on account of its common imperfections, and the other enumerated ma- "terials are hydroscopic in character and thereforevary from day to day infpoint of stiness and degree of resiliency.

Glass admits of being cemented to celluloid so intimately that it is impossible thereafter to Separate them without destroying the celluloid. This union can be effected by the application of heat and pressure, and by using a suitable cementitious or unifying ingredient. By reason of the heat and pressure required, the union can best be effected by employing comparatively thick pieces of glass, and it is possible to form a .sandwich, of which the three members are virtually in. a state of molecular adhesion and incapable of subsequent separation even when the glass isbroken and greatly fractured. It is feasible to use a sheet of `celluloid ranging in thickness from, say, twenty thousandths of an inch .down to around seven thousandths of an lnch, and lto"ei`ect i Ithe union under such conditions that the ultimate intervening layer of Celluloid will not be more than live thousandths of an inch in thickness and perhaps somewhat less.

Y This inventioncontemplates various rela' tions in the thickness of the three elements.

This will appear upon reference to the accompanying drawings, of which Fig. l is a side elevation of a tone arm embodying this diaphragm.

Figs. 2, 3 and 4 are cross sections of modified diaphragms, and Fig. 5 is a section through a sound box exemplifying the installation of the diaphragm.

Fig. 2 shows an intermediate stri of celluloid, exteriorly faced with two ayers of glass a and c. In this instance, the thick- -ness of the respective elements is so graduated that' the glass films are substantially one half the thickness of the celluloid. ln the form shown by Fig. 3, the glass facings a and c are of substantially the same thicklness as the intervening sheet b of Celluloid, whereas in Fig. tfthe plates of glass a" and' enclosed sheet of Celluloid b.

These diaphragms may be made by starting with glass and Celluloid of appropriate sizes and cementing them together to produce the ultimate article, but in case it is desired that the glass facings should be made quite thin, very perfect results can be obtained by making the diaphragm initially of plates ofl glass sufficiently thick to withstand any necessary pressure used in the formative process, and thereafter grinding down the glass plates until their thicknesses have been reduced to the required amount. It is not necessary to follow the grinding operation with a polishing step, although this can be done if desired, inasmuch as a very good acoustical result may be obtained by using ground glass. A handsomer appearance can, however, be obtained by polishing the glass, and the cost is not proc are each fifty per cent thicker than the After the diaphragms have been finished,

their edges may be bevelled as indicated in thel drawings, andthen they are centrally apertured and mounted. For example, as shown by Figs. 1 and 5, the diaphragm A is centrally apertured to receive a screw 6, which binds it to the extremity 5 of a vibrator 4, which' is actuated 'by the holder 3, which carries a thumb screw 2 for retaining a stylus 1. A little suitable wax or rosemetal solder 7 will prevent the screw 6 from shaking loose. |lihe diaphragm may be mounted in a conventional manner, as by placing it between two resilient` ringsl B, held in place by an annulus D against a holder C, which constitutes a part of the sound box carried by the sound tube l, which, in a Victor machine, is pivoted at F to a tone arm proper G.

llt will be perceived that this diaphragm is non-hydroscopic and, not easily broken7 being constructed of reinforced glass. lt furthermore possesses a very high degree of resiliency, owing to the permanent adhesion of its elements, and owing toy the fact that the least resilient element, to-wit, the celluloid, occupies the neutral zone whereas the active flexing regions are occupied by glass which, as is well known, is noted for its lack of elastic limit, i. e., its inability to take any permanent set under tension or compression. This diaphragm, therefore, not only uses materials of an entirely suitable nature and possessing proper -cha'racteristics for the purpose in hand, but these materials are disposed and united also in the manner best suitable for that purpose.

l therefore claim as my invention l. A diaphragm for recording or reproducing instruments composed of an intermediate sheet externally faced with glass intimately bonded thereto; the total thickness being such as easily to permit of flexure.

2. A flexural diaphragm consisting of an intermediate film of Celluloid and two films of glass externally applied thereto so as to be in a state of intimate adhesion to said Celluloid.

3. A flexural diaphragm consistingyof two thin plates of ground glass and an intermediate layer of Celluloid intimately bonded to said glass at all points of contact.

4. A sound box combining a flexural diaphragm consisting of Celluloid externally faced with glass, and a stylus secured centrally to said diaphragm.

ln witness whereof, hereunto subscribe my name, as attested by the two subscribing witnesses.

ALBERT l". NATHAN.

lVitnesses:

HELEN HENRY, LEON MINTZ. 

